NEWS

   1 Bison News
   2 ----------
   3
   4 Changes in version 1.75b:
   5
   6 * Bison now parses C99 lexical constructs like digraphs, UCNs, and
   7   backslash-newline within C escape sequences, as POSIX now requires.
   8
   9 Changes in version 1.75a, 2002-10-24:
  10
  11 * Bison can no longer be built by a K&R C compiler; it requires C89 or
  12   later to be built.  This change originally took place a few versions
  13   ago, but nobody noticed until we recently asked someone to try
  14   building Bison with a K&R C compiler.
  15
  16 * %error-verbose
  17   This new directive is preferred over YYERROR_VERBOSE.
  18
  19 * %lex-param, %parse-param
  20   These new directives are preferred over PARSE_PARAM and LEX_PARAM.
  21   In addition, they provide a means for yyerror to remain pure, and
  22   to access to the current location.
  23
  24 Changes in version 1.75, 2002-10-14:
  25
  26 * Bison should now work on 64-bit hosts.
  27
  28 * Indonesian translation thanks to Tedi Heriyanto.
  29
  30 * GLR parsers
  31   Fix spurious parse errors.
  32
  33 * Pure parsers
  34   Some people redefine yyerror to steal yyparse' private variables.
  35   Reenable this trick until an official feature replaces it.
  36
  37 * Type Clashes
  38   In agreement with POSIX and with other Yaccs, leaving a default
  39   action is valid when $$ is untyped, and $1 typed:
  40
  41         untyped: ... typed;
  42
  43   but the converse remains an error:
  44
  45         typed: ... untyped;
  46
  47 * Values of mid-rule actions
  48   The following code:
  49
  50         foo: { ... } { $$ = $1; } ...
  51
  52   was incorrectly rejected: $1 is defined in the second mid-rule
  53   action, and is equal to the $$ of the first mid-rule action.
  54
  55 Changes in version 1.50, 2002-10-04:
  56
  57 * GLR parsing
  58   The declaration
  59      %glr-parser
  60   causes Bison to produce a Generalized LR (GLR) parser, capable of handling
  61   almost any context-free grammar, ambiguous or not.  The new declarations
  62   %dprec and %merge on grammar rules allow parse-time resolution of
  63   ambiguities.  Contributed by Paul Hilfinger.
  64
  65   Unfortunately Bison 1.50 does not work properly on 64-bit hosts
  66   like the Alpha, so please stick to 32-bit hosts for now.
  67
  68 * Output Directory
  69   When not in Yacc compatibility mode, when the output file was not
  70   specified, running `bison foo/bar.y' created `foo/bar.c'.  It
  71   now creates `bar.c'.
  72
  73 * Undefined token
  74   The undefined token was systematically mapped to 2 which prevented
  75   the use of 2 by the user.  This is no longer the case.
  76
  77 * Unknown token numbers
  78   If yylex returned an out of range value, yyparse could die.  This is
  79   no longer the case.
  80
  81 * Error token
  82   According to POSIX, the error token must be 256.
  83   Bison extends this requirement by making it a preference: *if* the
  84   user specified that one of her tokens is numbered 256, then error
  85   will be mapped onto another number.
  86
  87 * Verbose error messages
  88   They no longer report `..., expecting error or...' for states where
  89   error recovery is possible.
  90
  91 * End token
  92   Defaults to `$end' instead of `$'.
  93
  94 * Error recovery now conforms to documentation and to POSIX
  95   When a Bison-generated parser encounters a syntax error, it now pops
  96   the stack until it finds a state that allows shifting the error
  97   token.  Formerly, it popped the stack until it found a state that
  98   allowed some non-error action other than a default reduction on the
  99   error token.  The new behavior has long been the documented behavior,
 100   and has long been required by POSIX.  For more details, please see
 101   <http://mail.gnu.org/pipermail/bug-bison/2002-May/001452.html>.
 102
 103 * Traces
 104   Popped tokens and nonterminals are now reported.
 105
 106 * Larger grammars
 107   Larger grammars are now supported (larger token numbers, larger grammar
 108   size (= sum of the LHS and RHS lengths), larger LALR tables).
 109   Formerly, many of these numbers ran afoul of 16-bit limits;
 110   now these limits are 32 bits on most hosts.
 111
 112 * Explicit initial rule
 113   Bison used to play hacks with the initial rule, which the user does
 114   not write.  It is now explicit, and visible in the reports and
 115   graphs as rule 0.
 116
 117 * Useless rules
 118   Before, Bison reported the useless rules, but, although not used,
 119   included them in the parsers.  They are now actually removed.
 120
 121 * Useless rules, useless nonterminals
 122   They are now reported, as a warning, with their locations.
 123
 124 * Rules never reduced
 125   Rules that can never be reduced because of conflicts are now
 126   reported.
 127
 128 * Incorrect `Token not used'
 129   On a grammar such as
 130
 131            %token useless useful
 132            %%
 133            exp: '0' %prec useful;
 134
 135   where a token was used to set the precedence of the last rule,
 136   bison reported both `useful' and `useless' as useless tokens.
 137
 138 * Revert the C++ namespace changes introduced in 1.31
 139   as they caused too many portability hassles.
 140
 141 * Default locations
 142   By an accident of design, the default computation of @$ was
 143   performed after another default computation was performed: @$ = @1.
 144   The latter is now removed: YYLLOC_DEFAULT is fully responsible of
 145   the computation of @$.
 146
 147 * Token end-of-file
 148   The token end of file may be specified by the user, in which case,
 149   the user symbol is used in the reports, the graphs, and the verbose
 150   error messages instead of `$end', which remains being the default.
 151   For instance
 152      %token YYEOF 0
 153   or
 154      %token YYEOF 0 "end of file"
 155
 156 * Semantic parser
 157   This old option, which has been broken for ages, is removed.
 158
 159 * New translations
 160   Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
 161   Croatian, thanks to Denis Lackovic.
 162
 163 * Incorrect token definitions
 164   When given `%token 'a' "A"', Bison used to output `#define 'a' 65'.
 165
 166 * Token definitions as enums
 167   Tokens are output both as the traditional #define's, and, provided
 168   the compiler supports ANSI C or is a C++ compiler, as enums.
 169   This lets debuggers display names instead of integers.
 170
 171 * Reports
 172   In addition to --verbose, bison supports --report=THINGS, which
 173   produces additional information:
 174   - itemset
 175     complete the core item sets with their closure
 176   - lookahead
 177     explicitly associate lookaheads to items
 178   - solved
 179     describe shift/reduce conflicts solving.
 180     Bison used to systematically output this information on top of
 181     the report.  Solved conflicts are now attached to their states.
 182
 183 * Type clashes
 184   Previous versions don't complain when there is a type clash on
 185   the default action if the rule has a mid-rule action, such as in:
 186
 187       %type <foo> bar
 188       %%
 189       bar: '0' {} '0';
 190
 191   This is fixed.
 192
 193 * GNU M4 is now required when using Bison.
 194 \f
 195 Changes in version 1.35, 2002-03-25:
 196
 197 * C Skeleton
 198   Some projects use Bison's C parser with C++ compilers, and define
 199   YYSTYPE as a class.  The recent adjustment of C parsers for data
 200   alignment and 64 bit architectures made this impossible.
 201
 202   Because for the time being no real solution for C++ parser
 203   generation exists, kludges were implemented in the parser to
 204   maintain this use.  In the future, when Bison has C++ parsers, this
 205   kludge will be disabled.
 206
 207   This kludge also addresses some C++ problems when the stack was
 208   extended.
 209 \f
 210 Changes in version 1.34, 2002-03-12:
 211
 212 * File name clashes are detected
 213   $ bison foo.y -d -o foo.x
 214   fatal error: header and parser would both be named `foo.x'
 215
 216 * A missing `;' at the end of a rule triggers a warning
 217   In accordance with POSIX, and in agreement with other
 218   Yacc implementations, Bison will mandate this semicolon in the near
 219   future.  This eases the implementation of a Bison parser of Bison
 220   grammars by making this grammar LALR(1) instead of LR(2).  To
 221   facilitate the transition, this release introduces a warning.
 222
 223 * Revert the C++ namespace changes introduced in 1.31, as they caused too
 224   many portability hassles.
 225
 226 * DJGPP support added.
 227
 228 * Fix test suite portability problems.
 229 \f
 230 Changes in version 1.33, 2002-02-07:
 231
 232 * Fix C++ issues
 233   Groff could not be compiled for the definition of size_t was lacking
 234   under some conditions.
 235
 236 * Catch invalid @n
 237   As is done with $n.
 238 \f
 239 Changes in version 1.32, 2002-01-23:
 240
 241 * Fix Yacc output file names
 242
 243 * Portability fixes
 244
 245 * Italian, Dutch translations
 246 \f
 247 Changes in version 1.31, 2002-01-14:
 248
 249 * Many Bug Fixes
 250
 251 * GNU Gettext and %expect
 252   GNU Gettext asserts 10 s/r conflicts, but there are 7.  Now that
 253   Bison dies on incorrect %expectations, we fear there will be
 254   too many bug reports for Gettext, so _for the time being_, %expect
 255   does not trigger an error when the input file is named `plural.y'.
 256
 257 * Use of alloca in parsers
 258   If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
 259   malloc exclusively.  Since 1.29, but was not NEWS'ed.
 260
 261   alloca is used only when compiled with GCC, to avoid portability
 262   problems as on AIX.
 263
 264 * When the generated parser lacks debugging code, YYDEBUG is now 0
 265   (as POSIX requires) instead of being undefined.
 266
 267 * User Actions
 268   Bison has always permitted actions such as { $$ = $1 }: it adds the
 269   ending semicolon.  Now if in Yacc compatibility mode, the semicolon
 270   is no longer output: one has to write { $$ = $1; }.
 271
 272 * Better C++ compliance
 273   The output parsers try to respect C++ namespaces.
 274   [This turned out to be a failed experiment, and it was reverted later.]
 275
 276 * Reduced Grammars
 277   Fixed bugs when reporting useless nonterminals.
 278
 279 * 64 bit hosts
 280   The parsers work properly on 64 bit hosts.
 281
 282 * Error messages
 283   Some calls to strerror resulted in scrambled or missing error messages.
 284
 285 * %expect
 286   When the number of shift/reduce conflicts is correct, don't issue
 287   any warning.
 288
 289 * The verbose report includes the rule line numbers.
 290
 291 * Rule line numbers are fixed in traces.
 292
 293 * Swedish translation
 294
 295 * Parse errors
 296   Verbose parse error messages from the parsers are better looking.
 297   Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
 298      Now: parse error: unexpected '/', expecting "number" or '-' or '('
 299
 300 * Fixed parser memory leaks.
 301   When the generated parser was using malloc to extend its stacks, the
 302   previous allocations were not freed.
 303
 304 * Fixed verbose output file.
 305   Some newlines were missing.
 306   Some conflicts in state descriptions were missing.
 307
 308 * Fixed conflict report.
 309   Option -v was needed to get the result.
 310
 311 * %expect
 312   Was not used.
 313   Mismatches are errors, not warnings.
 314
 315 * Fixed incorrect processing of some invalid input.
 316
 317 * Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
 318
 319 * Fixed some typos in the documentation.
 320
 321 * %token MY_EOF 0 is supported.
 322   Before, MY_EOF was silently renumbered as 257.
 323
 324 * doc/refcard.tex is updated.
 325
 326 * %output, %file-prefix, %name-prefix.
 327   New.
 328
 329 * --output
 330   New, aliasing `--output-file'.
 331 \f
 332 Changes in version 1.30, 2001-10-26:
 333
 334 * `--defines' and `--graph' have now an optionnal argument which is the
 335   output file name. `-d' and `-g' do not change, they do not take any
 336   argument.
 337
 338 * `%source_extension' and `%header_extension' are removed, failed
 339   experiment.
 340
 341 * Portability fixes.
 342 \f
 343 Changes in version 1.29, 2001-09-07:
 344
 345 * The output file does not define const, as this caused problems when used
 346   with common autoconfiguration schemes.  If you still use ancient compilers
 347   that lack const, compile with the equivalent of the C compiler option
 348   `-Dconst='.  autoconf's AC_C_CONST macro provides one way to do this.
 349
 350 * Added `-g' and `--graph'.
 351
 352 * The Bison manual is now distributed under the terms of the GNU FDL.
 353
 354 * The input and the output files has automatically a similar extension.
 355
 356 * Russian translation added.
 357
 358 * NLS support updated; should hopefully be less troublesome.
 359
 360 * Added the old Bison reference card.
 361
 362 * Added `--locations' and `%locations'.
 363
 364 * Added `-S' and `--skeleton'.
 365
 366 * `%raw', `-r', `--raw' is disabled.
 367
 368 * Special characters are escaped when output.  This solves the problems
 369   of the #line lines with path names including backslashes.
 370
 371 * New directives.
 372   `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
 373   `%debug', `%source_extension' and `%header_extension'.
 374
 375 * @$
 376   Automatic location tracking.
 377 \f
 378 Changes in version 1.28, 1999-07-06:
 379
 380 * Should compile better now with K&R compilers.
 381
 382 * Added NLS.
 383
 384 * Fixed a problem with escaping the double quote character.
 385
 386 * There is now a FAQ.
 387 \f
 388 Changes in version 1.27:
 389
 390 * The make rule which prevented bison.simple from being created on
 391   some systems has been fixed.
 392 \f
 393 Changes in version 1.26:
 394
 395 * Bison now uses automake.
 396
 397 * New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
 398
 399 * Token numbers now start at 257 as previously documented, not 258.
 400
 401 * Bison honors the TMPDIR environment variable.
 402
 403 * A couple of buffer overruns have been fixed.
 404
 405 * Problems when closing files should now be reported.
 406
 407 * Generated parsers should now work even on operating systems which do
 408   not provide alloca().
 409 \f
 410 Changes in version 1.25, 1995-10-16:
 411
 412 * Errors in the input grammar are not fatal; Bison keeps reading
 413 the grammar file, and reports all the errors found in it.
 414
 415 * Tokens can now be specified as multiple-character strings: for
 416 example, you could use "<=" for a token which looks like <=, instead
 417 of chosing a name like LESSEQ.
 418
 419 * The %token_table declaration says to write a table of tokens (names
 420 and numbers) into the parser file.  The yylex function can use this
 421 table to recognize multiple-character string tokens, or for other
 422 purposes.
 423
 424 * The %no_lines declaration says not to generate any #line preprocessor
 425 directives in the parser file.
 426
 427 * The %raw declaration says to use internal Bison token numbers, not
 428 Yacc-compatible token numbers, when token names are defined as macros.
 429
 430 * The --no-parser option produces the parser tables without including
 431 the parser engine; a project can now use its own parser engine.
 432 The actions go into a separate file called NAME.act, in the form of
 433 a switch statement body.
 434 \f
 435 Changes in version 1.23:
 436
 437 The user can define YYPARSE_PARAM as the name of an argument to be
 438 passed into yyparse.  The argument should have type void *.  It should
 439 actually point to an object.  Grammar actions can access the variable
 440 by casting it to the proper pointer type.
 441
 442 Line numbers in output file corrected.
 443 \f
 444 Changes in version 1.22:
 445
 446 --help option added.
 447 \f
 448 Changes in version 1.20:
 449
 450 Output file does not redefine const for C++.
 451
 452 Local Variables:
 453 mode: outline
 454 End:
 455
 456 -----
 457
 458 Copyright (C) 2001, 2002 Free Software Foundation, Inc.
 459
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